Presented in illustrated form:
; cat foo #!/bin/sh cat "$@" ; ./foo /etc/termcap | sed 1q >/dev/null ./foo: line 2: 3632 Broken pipe cat "$@"
This behavior is new in Bash 2, as far as I know. I find it extremely irritating, because programs having broken pipes is perfectly normal in Unix. Many filters and so on don't consume all of their input, and no other implementation of the Bourne shell reports this (as far as I know).
(I would not mind so much if this was only reported for
interactive sessions; it is that
bash spews out this
message in shell scripts that irritates me so much.)
As the BASH FAQ covers in its section E2, this can be disabled when people compile bash. Debian apparently usually compiles bash this way (good for them); Red Hat does not (sigh). Of course this solution only helps people who can recompile and reinstall bash on all of the systems they want their shell scripts to run nicely on.
You can muzzle much of the verbosity of this by adding a do-nothing
trap for SIGPIPE. Unfortunately you can't get it all; the
best you can do is:
; cat foo2 #!/bin/sh trap ':' 13; cat "$@"; exit 0 ; ./foo2 /etc/termcap | sed 1q >/dev/null Broken pipe
The message comes from
bash itself. If you
trap signal 13 to nothing
at all, bash will set SIGPIPE to 'ignored' (
SIG_IGN) for all of the
processes in the pipe, which will cause them to see write errors instead
of dying when the pipe breaks, which gets you:
; cat foo3 #!/bin/sh trap '' 13; cat "$@"; exit 0 ; ./foo3 /etc/termcap | sed 1q >/dev/null cat: write error: Broken pipe
Which error message you prefer is a matter of taste. I tend to
go for the
foo3 case, because at least then I can remember why
I am getting these strange messages (and grind my teeth about it
Comments on this page:Written on 07 April 2006.